What can I do against noise or humming during landline calls via an analogue telephone line?
There are a number of possible causes for a clearly audible noise or humming sound during calls with a telephone connected to the router, e.g. a defect in the telephone or the router. It is not due to the VoIP telephone connection, as the digital technology we use cannot rustle or hum. You would rather perceive interference, e.g. due to insufficient bandwidth, as distortion.
In order to determine the concrete cause of the noise or hum, please carry out the measures described here one after the other.
After each action, please check whether the noise or hum can still be heard. As soon as this is no longer the case, you no longer need to carry out the following measures.
Ruling out faults with the telephone
First, check whether your telephone is faulty. To do this, simply use another telephone connected to your router.
If you are using a cordless telephone (DECT telephone) connected to your router, please move the telephone’s base station further away from the router.
Check the router’s firmware
Step 1:
Please access the router’s user interface in a web browser. To do this, please enter your router’s IP address into the web browser’s address bar.
Step 2:
Please check the home page to see which firmware version is installed.
Step 3:
If you have a firmware version that has not been updated for over a year, please carry out a firmware update.
Rule out faults caused by other connected devices
Turn the device’s power adaptor halfway round in the socket so that the plug pins are now inserted into the opposite holes in the socket.
Check whether interference is reaching the router via a USB or LAN connection, or whether it can be diverted via these connections.
If one or more devices are connected to a USB or LAN port on the router, please remove all cables from the router’s USB and LAN ports for testing purposes. If no device is currently connected to a USB or LAN port on the router, please connect a computer to the router for testing.
Please establish a telephone connection. If you can no longer hear any hissing or humming, the cause was the power supply unit of another device or a so-called ground loop. In this case, the interference either reaches the router via the now-disconnected USB or LAN cable, or is conducted away from the router via the now-connected cable.
To resolve this, please connect your router and all devices connected to it to the same mains socket. Please try different sockets and/or a different power strip.
If a connected device is causing the noise or humming, please connect the device to the router using UTP-R45 cables (e.g. the ISDN/analogue cable). UTP-R45 cables, which are available from specialist retailers, do not have a ground wire and therefore do not transmit interference to the router.